1. Field of the Invention
The present invention relates to an apparatus for picking-up flat workpieces lying in a stack such as sheet metal plates, and for feeding them to a nearby processing station.
In various industries, it is required to be able to lift flat workpieces such as then plates which have a broard expanse but only slight stiffness, from a stack and to feed them individually to a processing station e.g. to plate shears or a press where a cutting or pressing step is carried out. The feed to the processing station is still effected nowadays largely by hand, and in order to avoid this monotonous and labour intensive work, various automatically-working apparatus have been proposed.
2. Description of the Prior Art
It is already known to provide apparatus in which a lifting device, arranged above the stack and equipped with suction lifters, is used for grasping and for raising the uppermost workpiece to a next device for transporting the raised workpiece. The raised workpiece is then grasped by magnetic rollers, which conduct the workpiece to a conveyor for forwarding it to the processing station.
Another known lifting device is provided with pneumatic suckers and is of mobile construction.
All these apparatuses mechanically complicated, require frequent adjustment and work unreliably. Particular difficulties arise in the take-over of the raised workpiece by the magnetic rollers and conducting it to a conveying device which feeds the individual sheet-metal workpieces to the processing station.
Further difficulties arise from the fact that mutual adhesion between the individual sheet-metal workpieces may result in the raising of the uppermost plate being accompanied by raising of the plate lying therebelow.